1. Field of the Invention
The present invention relates to a circuit for driving a gate of an insulated gate bipolar transistor (hereinafter abbreviated IGBT) inverter, and more particularly, to a single power gate driving circuit in an IGBT inverter which enables to drive a gate at a long distance by removing a noise generated as a gate driving distance gets long.
2. Background of the Related Art
FIG. 1 illustrates an equivalent circuit of a general IGBT device. In a single power driving method, a positive voltage or a zero voltage is applied to an IGBT inverter. But, in a dual power driving method, a positive voltage or a zero voltage, or a negative voltage is applied to an IGBT device.
When a DC voltage is applied across gate and emitter in the single power driving method, collector and emitter are electrically connected each other. When a zero voltage is applied between gate and emitter, collector and emitter are electrically disconnected. In other words, the IGBT device carries out a switching operation in accordance with a gate-applied voltage. In this case, xe2x80x98Ccexe2x80x99, xe2x80x98Ccgxe2x80x99, and xe2x80x98Cgexe2x80x99 indicate equivalent capacitances existing minutely between the respective terminals (collector-emitter, collector-gate, and gate-emitter).
Generally, the dual power driving method is used for a DC power source for driving a gate of the IGBT inverter. Yet, the dual power driving method fails to simplify the relatively complicated circuit construction, reduce the size of the inverter, and decrease the species of the voltages to reduce a cost. Accordingly, the single power driving method using the positive or zero voltage is commercialized.
FIG. 2 illustrates a general switching device using IGBT.
Referring to FIG. 2, a switching device using IGBT includes a first IGBT 1 of which collector is connected to a DC voltage Vdc and a second IGBT 2 of which collector is connected to an emitter of the first IGBT 1 and of which emitter is connected to a ground GND. When DC driving signals 3 and 4 having polarities opposite to each other are applied to gates of the first or second IGBTs 1 and 2 respectively, an output signal Vout is outputted from a connection point between the first and second IGBTs 1 and 2. In this case, the circuit shown in FIG. 2 represents an inverter circuit in part.
The switching device using the above-constructed IGBTs carries out xe2x80x98ONxe2x80x99 and xe2x80x98OFFxe2x80x99 of the first and second IGBTs 1 and 2 by the DC driving signals applied to the gates of the first and second IGBTs 1 and 2 so as to output the output signal Vout having the DC voltage Vdc or a voltage of the ground GND.
The above operational control is explained in detail as follows.
First, when the first IGBT 1 turns xe2x80x98ONxe2x80x99 and the second IGBT 2 turns xe2x80x98OFFxe2x80x99 by the DC driving signals 3 and 4, the output signal Vout becomes the DC voltage Vdc.
On the other hand, when the first IGBT 1 turns xe2x80x98OFFxe2x80x99 and the second IGBT 2 turns xe2x80x98ONxe2x80x99 by the DC driving signals 3 and 4, the output signal Vout becomes the ground voltage GND, that is zero voltage. Thus, the first and second IGBTs 1 and 2 carries out the xe2x80x98ONxe2x80x99 and xe2x80x98OFFxe2x80x99 controls, thereby enabling to mainly carry out the function of an inverter.
In this case, the DC driving signals 3 and 4 should prevent the first and second IGBTs 1 and 2 from turning xe2x80x98ONxe2x80x99 simultaneously. If both of the IGBTs turned xe2x80x98ONxe2x80x99, the DC voltage Vdc and ground GND are shorted to allow a large flow of a current, thereby breaking down the IGBTs 1 and 2. Thus, the DC driving signals 3 and 4 should have polarities opposite to each other absolutely. Moreover, the voltage applied between the gate and emitter of the first and second IGBTs 1 and 2 should be higher than a threshold voltage so as to drive the inverter.
FIG. 3 illustrates an IGBT inverter according to a prior art.
Referring to FIG. 3, an IGBT inverter according to a prior art includes a first IGBT 11 of which collector is connected to a DC voltage Vdc, a second IGBT 12 of which collector is connected to an emitter of the first IGBT 11 and of which emitter is connected to a ground GND, a first driving circuit 13 connected between gate and emitter of the first IGBT 11 so as to supply the gate of the first IGBT 11 with a driving voltage Vge through a first resistor R1, and a second driving circuit 14 connected between gate and emitter of the second IGBT 12 so as to supply the gate of the second IGBT 12 with a driving voltage Vge through a second resistor R2. In this case, an output signal Vout is outputted from a connection point between the first and second IGBTs 11 and 12.
The above-constructed IGBT inverter according to a prior art, as explained in FIG. 2, controls xe2x80x98ONxe2x80x99 and xe2x80x98OFFxe2x80x99 of the first and second IGBTs 11 and 12 by applying the DC driving voltages between the gates and emitters of the first and second IGBTs through the first and second driving circuits 13 and 14, respectively.
In this case, it is able to control speeds of xe2x80x98ONxe2x80x99 and xe2x80x98OFFxe2x80x99 between the collectors and emitters of the first and second IGBTs 11 and 12 respectively by adjusting current values applied to the gates of the first and second IGBTs 11 and 12 by setting up values of the first and second resistors R1 and R2 respectively. When the first or second IGBT 11 or 12 turns xe2x80x98ONxe2x80x99, voltages between the collectors and emitters are determined in accordance with the levels of the DC voltages applied thereto through the first and second driving circuits 13 and 14.
In case that the first and second IGBTs 11 and 12 are xe2x80x98ONxe2x80x99 and xe2x80x98OFFxe2x80x99 respectively or xe2x80x98OFFxe2x80x99 and xe2x80x98ONxe2x80x99 respectively, operations of the IGBT inverter according to a prior art will be explained in detail by referring to FIG. 4 and FIG. 5 in the following description.
FIG. 4 illustrates an operation of the first IGBT 11 in FIG. 3.
Referring to FIG. 4, the first IGBT 11 turns xe2x80x98ONxe2x80x99 when the driving voltage is applied thereto at a time point of t1. In this case, when the DC voltage Vdc is applied between the collector and emitter of the second IGBT 12, an output current I1 flows toward an output voltage terminal and a current I2 charging the equivalent capacitance Cge between the gate and emitter through the equivalent capacitance Ccg between the collector and gate of the second IGBT 12 is generated, simultaneously. Thus, a noise is generated from a driving signal of the second IGBT 12 during a short time for which electric charges charged in the equivalent capacitance Cge between the gate and emitter are discharged to the ground GND.
FIG. 5 illustrates an operation of the second IGBT 12 in FIG. 3.
Referring to FIG. 5, the second IGBT 12 turns xe2x80x98ONxe2x80x99 when the driving voltage is applied thereto at a time point of t2. In this case, when the DC voltage Vdc is applied between the collector and enitter of the first IGBT 11, an output current I1 flows from the output voltage terminal to the ground GND. At the same time, a current I2 charging the equivalent capacitance Cge between the gate and emitter through the equivalent capacitance Ccg between the collector and gate of the first IGBT 11 is generated. Thus, a noise is generated from a driving signal of the first IGBT 11 during a short time for which electric charges charged in the equivalent capacitance Cge between the gate and emitter are discharged to the ground GND.
As mentioned in the above explanation, the IGBT inverter according to the prior art, when the noise generated from the driving signal of the first or second IGBT gate exceeds the threshold voltage, makes both of the first and second IGBTs turn xe2x80x98ONxe2x80x99 so as to short the DC voltages and the ground each other. Therefore, a large current flows therebetween so as to break down the IGBTs.
Unfortunately, the IGBT inverter according to the prior art has difficulty in minimizing a gate driving distance not to make the noise exceed the threshold voltage as well as selecting the gate driving resistors and the driving circuits.
Accordingly, the present invention is directed to a circuit for driving a gate of an IGBT inverter that substantially obviates one or more problems due to limitations and disadvantages of the prior art.
An object of the present invention is to provide a circuit for driving a gate of an IGBT inverter having no difficulty in selecting gate driving resistors and circuits as well as adjusting gate driving distances freely.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a circuit for driving a gate of an IGBT inverter according to the present invention includes a first IGBT of which collector is connected to a DC voltage source, a second IGBT of which collector is connected to an emitter of the first IGBT, wherein an output signal is outputted from a connection point between the collector of the second IGBT and the emitter of the first IGBT, and of which emitter is connected to a ground, first and second driving circuits supplying across gates and the emitters of the first and second IGBTs with DC driving voltages, respectively, through first and second gate resistors, and first and second noise interruption circuits connected between the gates-emitters of the first and second IGBTs and the first and second driving circuits, respectively, so as to interrupt noises.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.